diff --git a/erpnext/crm/report/opportunity_summary_by_sales_stage/opportunity_summary_by_sales_stage.py b/erpnext/crm/report/opportunity_summary_by_sales_stage/opportunity_summary_by_sales_stage.py
index d2fc4ca849b..4f041d8da4b 100644
--- a/erpnext/crm/report/opportunity_summary_by_sales_stage/opportunity_summary_by_sales_stage.py
+++ b/erpnext/crm/report/opportunity_summary_by_sales_stage/opportunity_summary_by_sales_stage.py
@@ -153,15 +153,14 @@ class OpportunitySummaryBySalesStage:
 			}[self.filters.get("based_on")]
 
 			if self.filters.get("based_on") == "Opportunity Owner":
-				if (
-					d.get(based_on) == "[]"
-					or d.get(based_on) is None
-					or d.get(based_on) == "Not Assigned"
-					or d.get(based_on) == ""
-				):
+				value = d.get(based_on)
+				if not value or value in ["[]", "null", "Not Assigned"]:
 					assignments = ["Not Assigned"]
 				else:
-					assignments = json.loads(d.get(based_on))
+					try:
+						assignments = json.loads(value)
+					except json.JSONDecodeError:
+						assignments = ["Not Assigned"]
 
 				sales_stage = d.get("sales_stage")
 				count = d.get(data_based_on)